A deeper more holographic soundstage.

A piano in a room has depth. How BIG is the church and how big is the room? Once you can sense that, you know your can be happy about your system’s ability to reproduce depth.

The answer to the OP: Phase. Do phase well (especially out of phase information) and you get "depth."

Very good remarks...

I concluded that my acoustic treatment and control were right when i was able to hear this difference between the relative size of different recording live location, being it a small room or a church, i will add with the same perfect imaging in the 2 case...

Doing phase right for me was by listening experiments installing different acoustic devices or surfaces to make the waves timing with one another.... That ask for some balance between reflective, absorbing and diffusive surface....But also using resonators of different size....

Room treatment...you can use acoustic foam at all the early reflection points.  That means ceiling and floor too if possible. Use the mirror trick. This the cheapest and most effective. However WAF is zero.

Super tweeters don't work for this purpose. I have a pair of Townshend's lying in the cupboard.

Biggest jump up I had in creating a large soundstage was HFT's from Synergistic Research.  

Tunable resonaters are good, especially in combination with HFT's.  Need minimum two, more is better.

Synergistic Research make a very good one, I've forgotten what they call it, but it  has settings for many different ambiances and according to Jonathan Valin, it really works. Expensive though, around 3K...

Biggest jump up I had in creating a large soundstage was HFT’s from Synergistic Research.

I already speak about resonators in acoustic controls.... But instead paying big money i bought copper lure for fishing line among others things for few cent and try different size of other copper little bells with success...

Other active device controls would do marvel also at peanuts costs...

 I use it to ionize my air room and the effect is astounding, on par at least with my active Schumann generators grid (10 bucks by pieces)


Sometimes i think that placebo effect work by pricing the object costly and waiting for selling it...It is way evident with costly acoustical materials...If somewthing work it is NOT because his brand name is costly sometimes....i never bought specialized acoustic materials but chose by listening experiments with completely cheap one and my room is like a costly hall soundwise....


😁

Source can make a big difference: I was comparing two CD players. Same CD in each. same interconnects with both players played simultaneously- switching line inputs from the remote meant A/B blind testing was easy.

The main difference between the two was the 3D soundstage. One (a nearly top of the range Naim) had a wide but flat soundstage . The other (Vitus) went back way behind the speakers in an incredibly deep way. So please do not discount source.

When I replaced my BAT VK5i and 150 SE monoblocks to the new setup, my sound stage shrunk big time. BAT is known for big and deep sound stage, but I didn’t expect I would lose over 50% of the depth and 1/4 of width. So the equipment is important. I changed PC, IC, and speaker cables. They made less than 5% difference. 
I moved the speakers further away from the back wall and pointed them outward and that helped. But you can only do so much before the soundstage losing it’s focus. So I agree equipment may be the most important factor.